This invention relates in general to wind turbine systems and in particular to a floating wind turbine system.
Wind turbine systems convert the energy in moving air into other useful forms of energy, usually electricity. Prior art wind turbine systems usually include a wind generator driven by rotor blades and rotatably mounted upon an upper end of a vertical support tower such that the rotor may be rotated relative to the tower as the wind direction changes such that the rotor blades are maintained perpendicular to the wind. Over the past twenty-five years, wind turbine systems have established themselves as reliable systems in widespread use throughout the world. The vast majority of these wind turbine systems have been installed on land with the lower ends of the support towers extending into the ground for stability.
In the past few years, some wind turbine systems have been installed in waters offshore of land to capture higher wind speeds as well as for other advantages. These offshore wind turbines use support towers and foundations that are similar to those on land. Such current offshore technology is limited to water depths of about 25 meters or less. Installation costs for these offshore sites are significantly higher than on land because of the increased effort required while working on and in the water.
Concepts for deeper water installations that are currently under development are mostly derived from configurations for offshore oil well rigs to include floating platforms. Accordingly, such concepts typically require large cranes for erection of the towers and turbines and are not optimal for wind turbines because of the large aerodynamic force in the direction of the wind as well as forces associated with dynamics from the angular momentum of the turbine blades. Furthermore, wind and wave forces cause coupled motions of the support tower and the rotor blades, resulting in greater structural dynamic loads, deflections and stresses upon the wind turbine system. Therefore, it would be desirable to provide an offshore wind turbine system that not only is adaptable to the wind and wave forces, but also is easily installed in deep water locations.